MirOS #8, #9, #10, #10-current: It is advised
to refrain from using the
ext2fs filesystem, especially in read-write mode,
because symlink code is broken. The filesystem, and all processes
accessing it, become unresponsive (hang in D state) upon creation
of a symbolic link or access of a filesystem where such a broken
symlink(7) is created. MirOS #7 can be used to access filesystems
such as these, but the broken symlinks can still not be accessed
by penalty of a kernel panic(9).

MirOS #10-current: ext2fs will be mounted read-only by default
for now, starting 2009-04-23, until these problems are fixed.

MirOS (recent but unknown versions): the async mount
flag ceased to work as it did before, says bsiegert@